1. Field of the Invention
The present invention relates to an article carrying apparatus for carrying articles by utilizing pressure of fluid such as compressed air.
2. Description of the Related Art
An article carrying apparatus of this type is described, for example, in Japanese Utility Model Laid-Open Publication 60-110169. This apparatus comprises a cylinder tube of a given length, a piston movably arranged in the cylinder tube, a moving piece freely moving along an outer peripheral surface of the cylinder tube, and a magnet coupling each mounted on the piston and the moving piece and attracting each other. When an article is held by the moving piece in this article carrying apparatus and the piston is moved by supplying and discharging pressure fluid to and from the cylinder tube, the moving piece is moved after the piston by attracting force of the magnet couplings, and the article is moved.
It is important in the article carrying apparatus of this type that the moving piece is not deviated upward, downward, leftward or rightward due to the weight of the article to be carried or that it is not tilted due to the center of gravity of the article. If such deviation or tilting occurs, it is not possible to ensure smooth movement of the moving piece and this causes trouble in carrying the article.
In this respect, it is essential that the moving piece is moved always in a stable posture. For this purpose, it is desirable to support the moving piece on a guide, which extends along the cylinder tube, thereby limiting its movement in the upward, downward, leftward and rightward directions and also preventing it from tilting and that the moving piece is moved along the guide and the cylinder tube under this condition.
However, when the moving piece is supported on the guide in such a manner that its movement is restricted in all directions except the axial direction, the moving piece may be caught by the guide or the cylinder tube and may not move further if there is an error in a manufacturing dimension or on assembling dimension of each component in case where the guide and the cylinder tube are independently manufactured and assembled because the moving piece is closely fitted to the cylinder tube and its movement is restricted in all directions except the axial direction.